Oculex will develop an injectable biodegradable biocompatible intraocular controlled-release drug delivery system for the treatment of cytomegalovirus retinitis associated with AIDS. The antiviral drug is contained in biodegradable biocompatible polymeric microparticles, which are administered via syringe into the vitreous of the patient by an ophthalmologist. Once in place in the vitreous, the microparticles provide a programmed controlled-release of the drug for a predetermined time interval, establishing a therapeutically effective drug concentration level. After delivering their drug load, the microparticles degrade into benign compounds that are readily absorbed by the body. In Phase I Oculex proposes to demonstrate the feasibility: 1. Manufacturing controlled-release polymeric microparticles no larger than 50 micro m with drug loads between 5 and 15wt%. 2. Developing a delivery system with an average in vitro drug release rate of approximately 1 microgram/h lasting at least one month. Phase II will focus on extending the time of delivery to achieve a balance among medical, technical, and marketing factors, Phase II will also include the accumulation of data to support an Investigational New Drug (IND) Application with the US Food and Drug Administration.